Updated: Jul 27
If you are considering hormone therapy, you are undoubtedly concerned about everything you have heard about estrogen and breast cancer risk. The World Health Initiative (WHI) study on hormone replacement and breast cancer was stopped in 2002; due to a non-statistically significant increase in invasive breast cancer and an increase in heart disease adverse events. Following that, there was an explosion of media coverage about the study. Doctors all over the country advised their female patients to withdraw from hormone treatment, despite multiple previous studies that contradicted the findings of the WHI study.
Since that study, the results of the WHI study have been challenged. Subsequent studies have contradicted the WHI study, but the damage was done. Even to this day, there is a pervasive belief that estrogen increases the risk of breast cancer, when in fact, it has a protective effect. Unless you are willing to take a deep dive into the science, it can be hard to know who to believe and what to do.
At Optimal Hormone Health, our job is to know the science and apply all of the known principle effects of hormone replacement for your particular situation. Let’s take a look at some of the past and more recent research. We are taking much of our information from Dr. Lindsey Berkson’s ebook: Estrogen Vindicated. You can purchase her book here if you would like to take a closer look.
Previous Studies on Hormone Replacement
Multiple previous studies contradicted what the later WHI study reported. Some of the studies recommend hormone replacement for breast cancer protection:
In a 1993 editorial in the New England Journal of Medicine, two endocrinologists from Harvard stated, “On the basis of the available evidence, we recommend that all postmenopausal women be considered for hormone replacement therapy and be educated about its risks and benefits.”
Study after study found no consistent increased risk of breast cancer in women who took estrogen for five years, ten years, or 15 years. A later Japanese study on 9,000 women replicated this data. It is well accepted that through the 20th century, that estrogens did not cause breast cancer.
Problems with the WHI Study
Then came the WHI study and subsequent findings that the study was flawed for several reasons:
It only used one protocol of hormones (not individualized or diverse options)
The age of the participants was older, many years away from hormone exposure
The majority of women were obese (which is a significant risk factor for breast cancer)
A large number of dropouts of participants in the study
The recommendations could not be validly generalized to all women
Many of the WHI’s conclusions were ultimately found to be inaccurate.
Studies That Support Estrogen Use
Many of the studies that support estrogen use have not received much attention. Here are some of the Human Trials mentioned by Dr. Berkson in support of estrogen use:
At MD Anderson Cancer Center, a randomized prospective study gave 39 breast cancer survivors Premarin compared to 319 breast cancer patients not on estrogen. They were followed for 52 months and found no increased risk of recurrence in breast cancer patients on HRT.
A gynecologist at the University of California, Irvine, matched 125 breast cancer patients on ERT or HRT with 362 who did not receive hormones. There was no increased risk of recurrence in breast cancer patients on hormone therapies.
A cancer doctor reported a prospective study of 277 breast cancer survivors on ERT for an average of 3.7 years, matched with controls, and no increased risk of recurrence was found.
University of Texas Southwestern Medical Center compared 64 breast cancer survivors on ERT with 563 matched controls, not on ERT followed for an average of twelve years and found no increased risk of recurrence with hormonal therapies.
At the Fred Hutchinson Cancer Research Center at the University of Washington, they reviewed records of 2,755 women diagnosed with cancer between 1977 and 1999, 174 given HRT compared each to 4 controls and followed for an average of 3.7 years finding that HRT in breast cancer survivors had no adverse effect on recurrence or mortality. In fact, breast cancer survivors on HRT had significantly lower breast cancer recurrence rates, breast cancer mortality rates, and overall mortality rates compared to survivors, not on hormones.
The Medical College of Wisconsin conducted a review of nine independent observational studies and one randomized controlled trial and found that breast cancer survivors prescribed HRT had no significant risk of recurrence. Their meta- analysis had 717 survivors on HRT compared with 2,545 survivors not on HRT and they found 3% fewer deaths in survivors on ERT compared to 11.4% deaths in survivors not on hormones.
Researchers from Slovenia from the Institute of Oncology in Ljubljana, compared twenty-one women with breast cancer who were treated with HRT for an average of 28 months with controls for each patient. They found no increased recurrence of breast cancer among women on hormones.
University of South Wales reproductive endocrinology department followed 90 breast cancer survivors treated with HRT for an average of 18 months followed for an average of 7 years with 180 matched controls found a small but significant reduced recurrence of breast cancer among women on prescribed hormones205.
A gynecologist at the Women’s Health Institute of the Royal Hospital for Women compared 167 women surviving breast cancer on HRT compared with 1,122 similar women not given HRT. There were no increased recurrences of breast cancer even in ER+ patients. A four-year follow-up found that there was no increased risk of recurrence in breast cancer patients on HRT.
A gynecologist from the University of New South Wales published a retrospective observational study of 286 breast cancer patients prescribed HRT compared to 686 breast cancer survivors who didn’t get put on HRT, with some women followed for 26 years. Women on HRT had lower rates of recurrence. They concluded: HRT use for menopausal symptoms by women treated for primary invasive breast cancer is not associated with an increased risk of breast cancer recurrence or shortened life expectancy.
A cancer doctor at the Hospital Saint-Louis in Paris followed 120 breast cancer survivors prescribed HRT and each patient was compared to two matched control women and followed for 2.4 years. There was no increased risk of recurrence of breast cancer in survivors on hormones.
Researchers at the University Central Hospital from Helsinki followed 131 breast cancer survivors, 88 who took ERT and 43 who did not, for 2.6 years. There was no increased risk of recurrence in estrogen survivor users.
German researchers at the Friederih Alexander University in Erlangen retrospectively reviewed 185 breast cancer patients, 64 who took HRT and 121 who did not. After five years, there was no observed increased risk of recurrence.
What Are We to Conclude?
One conclusion? We need more studies to confirm that estrogen replacement does not increase breast cancer risk under ordinary circumstances. It is exceptionally challenging to assess scientific data that changes from study to study, but there are risk factors with every medication we take. For example, the risk factors of taking ibuprofen. No woman wants to increase her risk of breast cancer, but you should weigh those risks against the benefits of estrogen replacement which include:
Reduces risk of cardiovascular disease and stroke
Reduces the frequency and severity of hot flashes
May reduce the risk of Alzheimer’s disease
Prevention of bone loss
Better retention of collagen
Improved mood and cognition
Talk with us at Optimal Hormone Health about your concerns and your specific risk factors. You have the final say on what you want to do, and we support you in your decision. Our job, which we take seriously, is to stay apprised of the most recent research so we can advise you in your journey towards better health and well-being.